The present invention relates to an apparatus for testing for accuracy of machine tools and measuring devices, with a support and at least one reference element.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
In an apparatus available from the company Dreier Lasermesstechnik GmbH, Horb am Neckar, with the designation “Quickmaster”, for testing the accuracy of machine tools and measuring devices, in particular for testing the accuracy of the travel paths and positioning of tools and scanning means, a stone cuboid with several precisely positioned bores is employed. These bores are provided with sleeve-shaped inserts, in particular collar bushings, which are glued into the bores. After being glued, these bushings, in particular their interior surface, are ground with a high precision coordinate grinding machine and brought to a desired dimension. Which such a test apparatus, information can be provided within a short time and quickly about the state of a CNC machine tool, in particular about the accuracy and the zero point setting of the machine. This is particularly important for the manufacture of high-precision parts, when brief tests must be regularly performed on the machine tool, or when after a machine crash the accuracy of the machine must be checked. It is particularly important to know after a machine crash if the machine has changed with respect to geometry and positioning. With the known device, information about the state of the machine can be obtained within a short time and quickly. This saves service costs, reduces machine and production downtimes and production costs; moreover, insurance premiums need not be paid, because less insurance payouts are needed. With the conventional test apparatus, the flatness, parallelism and angular accuracy can be measured, with tolerances in a range of 2 μm.
It has been observed that the conventional test apparatus is temperature-sensitive and that cracks are formed in the support in the event of greater temperature variations. These cracks are created because the glued bushings have expanded more during heating than the support surrounding the bushings in which the bushings are glued. This may happen, for example, because such test apparatus is placed in a car and is not adequately protected from heat caused by incident solar radiation. As an additional disadvantage, the manufacturing expense of such test apparatus is relatively high, because first highly precise bores must be introduced in the support, in which the bushings are then glued, whereafter the bushings have to be micro-polished.
It would therefore be desirable and advantageous to address this problem and to obviate other prior art shortcomings by to providing a test apparatus which is less sensitive to temperature and which can be produced at lower cost and more quickly.